Method for producing titanium tetrachloride



March 15, 1960 E. A. MASON ETAL 2,923,724

METHOD FOR PRODUCING TITANIUM TETRACHLORIDE Filed Nov. 16, 1956 A 32... 838 Fm \nm .596 E Law 398 0 2362. m a 3 N s 3 a 553m fiuend Q II W I o m r 0 k\ km @(9 m .5235 M #55351 M Q G w fl a m 3 I d mw 525$ 5 63 ma ma. x 3 Q fi v m 1% Emma: .L Sm. :L WQ\ 93m 2856 United States Patent 2,928,724 METHOD FOR PRODUCING TETRACHLORIDE Edward A. Mason, Lexington, and Carolus M. Cobb, Lynn, Mass, assignors to Ionics, Incorporated, Cam-' bridge, Mass, a corporation of Massachusetts Application November 16-, 1956, Serial No. 623,726 4 Claims. (Cl. 2387) This invention relates to a method for producing titanium tetrachloride from titanium concentrates, ores and slags containing, calcium, magnesium, silicon and aluminum as contaminants. This application is a' continuation-impart of applicants application Serial No. 386,067, filed October 14, 1953, now abandoned;

Titaniferou's ores, and slags or concentrates such as result from the smelting of ilmenite and rutile ores have been chlorinated in the presence of substantial amounts of carbon by treatment with chlorine-containing gases; however, in order to obtain a practical rate of reaction, it has been necessary to utilize temperature above 700 C. and a preferred range of 850-1200" C. Owing to the high temperatures required, the titanium tetrachloride produced is generally found to be heavily contaminated with the chlorides of other metals, and further the reacting mass has been found to be agglutinated by the molten non-volatile alkaline earth chlorides formed during chlorination so as to present serious difiiculties in moving the reacting mass through the reactor and obtaining a high recovery of titanium values from the residual solids. It has also been found that owing to the low heat of reaction of the chlorination of a mixture of carbon and titaniferous materials, it has been ditficult to maintain the temperature of the reacting mass at 700 C. or higher without supplying additional heat by periodically burning off some of the carbon in the mass, by introducing superheated gases, or by external and/ or internal heat addition.

Various methods have been devised for overcoming the coating and sticking eiiect caused by operating at temperatures above the melting point of the alkaline earth chlorides; for example, by heating the titaniferous material with titanium phosphate or with phosphoric and sulfuric acids. a

This invention provides a new method of converting such ores and sla'gs 'to titanium tetrachloride in a most efficacious, economic and efficient manner, wherein cor rosion, frequent shut-downs, and loss of efiiciency are avoided and continuous operation is made possible. Furthermore, the TiCl, produced in accordance with the invention is characterized by its high purity which is very desirable in the subsequent production of titanium metal by processes well known per se.

One of the objects of the present invention is to provide a form of the titaniferous material which may be rapidly chlorinated at comparative low temperatures. Another object is to provide a process for producing titanium tetrachloride from titaniferous materials whereby Inetallic contaminants' previously encountered are substantially eliminated. A further object of the invention is to provide a process wherein the deleterious efiects caused by the presence'of alkalineearth metals in titaniferous mate'- rials are substantially eliminated. These and other objects will become apparent from the following description of the invention.

The present invention is particularly adaptable to increasing the rate of chlorination of titaniferous oxidic slag compositions such as are disclosed in US. Patent 2,476,453 andwhich result from electric furnacesmelting of'titanium ores such as ilmenite with the amount of carbon'c'ontrolle'd soas 'to produce a minimum reduction-of 't'lie titaniumvalues from the quadrival'ent-s'tate.

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While such oxidic slags have heretofore been chlorinated at comparatively low temperatures- (US. Patent No. 2,701,180),- the rate of chlorinationunder such conditions has been found to be inadequate and insufficient to sustain successful commercial operations. hand, the reactivity of the titanium element in slags produced according to the present invention has been found to he suiiicient to maintain commercially successful rates of fluidized bed chlorination.

In its broadest aspect this invention contemplates a process for producing titanium tetrachloride from titaniferous' ores, slags and concentrates, which also contain small amounts of compounds of calcium, magnesium, aluminum and silicon, by reacting the titaniferous mate rial with a carbonaceous reducing agent in certain minimum proportion, at temperatures above the melting point of the titaniferous material or at temperatures suiiicient to cause the evolution of carbon monoxide, comminuting the reaction product, and reacting the comminuted product by a fluidized-solids technique with a gaseous chlorinating agent at temperatures below about 500 C. More particularly, titaniferous materials are mixed or treated with a carbonaceous reducing agent in excess of 0.2 part carbon per part of titaniferous material, such as coal, coke, charcoal, residual fuel oils, coal gas, natural gas, etc. and heated at temperatures over. l000 C. and preferably 1300 to about 1500 C. Temperatures below 1300 C. would also be effective when the solid carbonaceous material and slag are compressed, or when gaseous reducing agents are employed. The resulting mass is cooled, comminuted and reacted with a gaseous chlorinating agent such as chlorine, phosgene, carbon tetrachloride, etc. with or without the presence of an inert gas, in a fluidized bed at a temperature between 200 and 500 C., and preferably between 300 and 500 C. The titanium tetrachloride formed is separated from the reacting mass by volatilization. chlorinating temperatures below 580 C. are efiective in our process and advantageous in preventing the chlorination of the contaminants of the titanium source material. chlorinating temperatures below 700 C. are effective in preventing the deleterious effects of agglutination referred to above.

By reacting the titaniferous material with a carbonaceous reducing agent in proper proportions, it has been found that an economically high subsequent chlorination rate may be obtained at comparatively low chlorination temperatures and that substantially little of the aluminum and silicon present are chlorinatedp Furthermore, the

deleterious effects of the alkaline earth chlorides are minimized in the chlorinating mass. The TiCl, produced in accordance with the invention is characterized by its high purity and high rate of production. 7

The invention will be further described with respect to the carbon-reduced slag is delivered through line 15 to.

the fluidized reactor 5. Chlorine and an inert gas, if employed, regulated in-proportions by valves 26 and 27 re spectively, are mixed and delivered to pre-heater 8 through the lines 16, 17, and '18 and then to the bottom of the fluidizer 5 through line 20.. The pre=heater-may be eliminated' by causing the chlorinating'g'as-toflow through by pa ss line '19. 'From thetop of the tliiidizer 5 -the gaseous products of the reaction are' passed through lin'e -22 intothe condenser'6 wherethe condens'ed{FiGhis enti- On the other i enclaves carbon dioxide, etc., are conveyed through line 24 for disposal and in some .cases for reuse (after proper purification, if required) to line 17 (not shown), The spent solids of the fluidized reactor are removed through line 21. V I

In operation the reaction of the titaniferous material with the carbonaceous reducing agent is carried out at, a temperature between 1300 and 1500 C. or higher and, preferably at or above the meltingpoint, of the titaniferous material. Suitable carbonaceous reducing agents are coal, graphite, coke, charcoal; petroleum oils, residual fuel oil, methane, ethane, and other hydrocarbon gases such as coal gas,'mixtures of hydrocarbons, or. evenhydrogen, etc. The titaniferousmaterials are preferably ground or otherwise comminuted' to pass 40 mesh sieve and are mixed with the carbonaceous reducing agent as a liquid, ,solid'or gas, and then heated in an induction, arc,

resistance, or other furnace at the temperature indicated above. In the event that a gaseous or volatile carbonaceous reducing agent is used, the comminuted titanium source material may be first preheated to the reaction temperature and the reducing material passed into the heated mass. The quantity of carbonaceous material employed is such that the carbon content of the reducing agent shall be in excess of 0.2 part by weightof the titanium source material and preferably not more than 0.7 part. It will be clear that the actual ratio of carbon titaniferous material, and employing a temperature of reaction above the melting point of said titaniferous material, or in excess of 1000 C. a

During the course of the reaction between the titanium source material and the reducing agent, considerable quantities of carbon monoxide will be evolvedand the commencement and termination of the reaction may be followed by the initiation or cessation of this evolution.

The resulting mass, containing lower, oxides of titanium as well as impure titanium carbide, is cooled and then comminuted by wellknown means, per se, and pulverized to the required particle size suitable for the design of the subsequent fluidized bed chlorination operation. Preferable particle sizes are in the range of 40-300 mesh'to provide easeof operation.

The comminuted and sized carbon-reduced material is then continuously inducted into the fluidized-solids re actor where it is suspended or fluidized in an upwardlymoving gaseous streamcontaining a chlorinating agent such as chlorine, phosgene,carbon tetrachloride, and the like. The reaction of the chlorinating agent with the reduced material is highly exothermic and in order to maintain the temperature of the reacting mass below about 500 C., thereby obtaining the desirable features of the present invention, it is necessary to. provide means for introducing or removing heat depending on the size of the reaction vessel and on the rates of introduction of the chlorinating agent and the reduced material. It is obvious that the reduced material-maybe maintained in a fluidized state and the rate-of reaction controlled by-regulating the concentration and/or the flow rate'of the chlorinatingagent in the gaseous suspending stream employing inert gases suchas nitrogen, flue gas, etc. as diluents. The reaction of the chlorinating agent with the reduced material proceeds rapidly at temperatures below 500 C evolving titanium tetrachloride and iron chlorides 4 (if iron is present). At the temperatures of the reaction the titanium chloride (and iron chloride) are carried out of the reaction vessel in a moving stream of gas and may be condensed out by cooling the gas in conventional equipment. It is, of course, often desirable to carry out a partial condensation in order first to remove the iron chlorides whereupon the final condensation may be carried out at temperatures to 0 C. or lower in order to substantially eliminate titanium tetrachloride from the residual gas stream. The chlorinated particles of the reduced material are lighter in weight than the unchlorinated particles and maybe continuously removed from the fluidized reactor by being carried out at the top of thereact'or in the moving gaseous stream and thereupon separated in conventional solid gas separators, such as cyclone'separators, and thereafter discarded. In the event that a diluent inert gas is used, this gas may be recovered and returned to the preheater after purification and drying.

. Methods which have been used for carrying out the process of this invention are describedin the following examples.

PRODUCTION OF CARBONACEOUS REDUCED SLAG A slag obtained from the recovery of iron from the smelting of a low-grade ilmenite ore said slag being known as Sorel or Quebec Iron and Titanium Corporation Slag having the approximal composition as follows:

Percent 7 Foo 9.9 A1 0 6.0 SiO 6.3 MgO 5.2 CaO 0.9 V 0 0.6 Fe 0.4

Minor parts other impurities.

" ratios as outlined above are equally efiective. This mixture was charged into a graphite-lined furnace. The furnace temperature was raised over the course of five to nine hours to approximately 1380 C., which was the approximate melting point of the slag, when the evolution of carbon monoxide was first observed. Heating was continued at atmospheric pressure for about five hours at a maximum temperature of about 1400 C. A similar homogeneous mixture of slag and carbon was similarly heated for approximately 6 /2 hours at amaximum tem perature of 1525 C. as summarized in the following table:

After the electric power was discontinued, the furnace was allowed to cool for two, to three days when the charge was removed. The solid products obtained were mixed and ground and screened to between 70 and 230 mesh size in preparation for chlorination using fluidized bed techniques as noted in the following examples:

Example 1 Approximately 200 parts of the prepared carbon-reduced slag were suspended in an. upwardly-moving gas stream in 'a Vycor glass reactor which was heated externally by means of electric Thegas stream consisted initially of nitrogen which had been pre-heated to about 400 C. Chlorine gas flow was initiated when the temperature of the fluidized solids reached 375 C., and the N flow was decreased so that the gas entering the bottom of the reactor consisted of a preheated mixture of 5.3 parts per minute of chlorine and 3.1 parts per minute of N The temperature in the reaction zone was maintained at 375 C. The purpose of the N diluent was to provide temperature control, but it should be understood that chlorine gas alone could be used providing other methods of temperature control are provided. The gaseous reaction products were carried out of the reactor by the flowing gas stream and passed through a condenser. Any iron chlorides present in the vapors were condensed and removed in the initial part of the condenser. The resulting TiCl product was obtained at a production rate of 4.9 parts per minute with better than 98% utilization of the chlorine feed. No agglutination of v the particles in the reactor occurred.

Example 2 p A preheated mixture of 6.8 parts per minute of chlorine and 2.5 parts per minute of N was used to suspend and chlorinate approximately 100 parts of carbon-reduced slag prepared above at a reaction temperature of 430 C. TiCL; was produced at a rate of 7.1 parts per minute and the chlorination utilization was better than 98%. No sticking of the particles in the reactor occurred.

In both Examples 1 and 2 above where temperatures of chlorination were maintained below 500 C., it was ascertained that the Ca and Mg in the TiCL, product was negligible nor were any detectable amounts of Si or Al present in the TiCl product.

Example 3 A preheated mixture of 7.2 parts minute of C1 and 1.5 parts per minute of N diluent was used to suspend approximately 150 parts of carbon-reduced slag prepared above. The temperature of the fiuidizer-reactor was maintained at 520 C. A production rate of 8.5 parts per minute of TiCl resulted and the chlorine utilization was virtually complete. No sticking of the particles in the reactor occurred. However, there was evidence of a slight removal of Si and Al from the reduced solids during chlorination. There was also evidence of some chlorination of Ca and Mg, but no sticking occurred since the temperature of the reaction was below the melting point of the chlorides of these metals.

In order to show the effect of operating the chlorination reaction at temperatures above the melting point of MgCl (melting point of 708" C.) 200 parts of the carbon-reduced slag described above that had been heated at 1525 C. was chlorinated, using a fluidized-bed technique by feeding preheated gas consisting of 22 parts per minute of chlorine and 7.3 parts per minute of N The reactor was maintained at a temperature of 730 C. A TiCl production rate of 20 parts per minute resulted. In this run considerable portions of the contaminants were removed from the reduced solids during chlorination. Furthermore, the solids in the reactor formed a scale on the inside wall of the reactor and an agglutination of the reaction mass was noted upon cooling of the reactor. The presence of this scale and evidence of a sticky mass pany Slag having the composition noted above and made in accordance with the procedure of the Pierce Patent No. 2,476,453 was obtained and mixed and with'additional carbon without further high temperature'carburization producing a carbon to slag ratio of approximately 0.4. This mixture without any further carburization reaction was suspended in preheated'chlorine gas at a rate of 13 parts per minute to 200 parts of said mixture of carbon and slag. The temperature of the fluidized reactor was maintained at 500 C. Aproduction rate of- 0.7 part per minute of TiCl, resulted;

(2) Preheated chlorine at a rate of 13 partsperminute was used to suspend 200 parts of a mixture of carbon and slag of (1) above. With the fluidized reactor temperature maintained at 750 C. a production rate of 1.2 parts per minute of TiCL; resulted.

(3) A carbon and slag mixture of (1) above was briquetted and crushed and treated as in (2) above. A production rate of 1.7 parts per minute of TiCL, resulted.

While partial and inadequate carbon-reduced slags, such as the slags of the Pierce patent above, have been chlorinated at comparative low temperatures, the rate of chlorination in such cases have been wholly inadequate fluidized-bed chlorination of the carburized slag of the to sustain any successful commercial operation.

"It will be apparent from the above that the rate of present invention far exceeded the fluidized-bed chlorination of prior titaniferous slags where uncarburized or insutficiently carburized slags were employed in the fluidized-bed chlorination'reaction at comparative low temperatures.

While this invention has been described and illustrated by the examples, shown, it is not intended to be strictly limited thereto and other modifications and variations may be employed within the scope of the following claims.

We claim:

1. A process for chlorinating titaniferous materials consisting of the concentrates, ores and slags of titanium, said titaniferous materials containing as contaminants at least one of the group consisting of aluminum, silicon, calcium, and magnesium, comprising the steps of reacting the material with a carbonaceous reducing agent in excess of 0.2 part by weight per part of titaniferous material at a temperature between 1000 C. and about 1500 C., cooling and comminuting the mass, chlorinating the resulting comminuted mass by suspending the same in a gaseous chlorinating agent in a fluidized reactor at a tempertaure maintained between 200 and 500 C., whereby the titanium content of the material is chlorinated and selectively removed with respect to said contaminates,

- and condensing the resulting volatile TiCl the latter are detrimental to the chlorination of the titanium values being substantially free from said contaminants of;the original titaniferous materials.

2. The process of claim 1 wherein the chlorinating agent is chlorine gas.

3. The process of claim 1 wherein the chlorinating agent is a mixture of C1 and an inert gaseous diluent.

4. The process of claim 3 wherein the gaseousdiluent is N2.

References Cited in the file of this patent UNITED STATES PATENTS 1,179,394 Barton Apr. 18, 1916 1,528,319 Carteret et a1. Mar. 3, 1925 2,184,884 Muskat et a1. Dec. 26, 1939 2,616,784 Reimert Nov. 4, 1952 2,701,179 McKinney Feb. 1, 1955 OTHER REFERENCES Barksdale: Titanium, Ronald Press Co., N.Y., 1949, pages 61 and 316.

Thornton: Titanium, TheChemical Catalog Co., Inc. N.Y., 1927, pages 46 and 52. 

1. A PROCESS FOR CHLORINATING TITANIFEROUS MATERIALS CONSISTING OF THE CONCENTRATES, ORES SLAGS OF TITANIUM, SAID TITANIFEROUS MATERIALS CONTAINING AS CONTAMINANTS AT LEAST ONE OF THE GROUP CONSISTING OF ALUMINUM, SILICON, CALCIUM AND MAGNESIUM, COMPRISING THE STEPS OF REACTING THE MATERIAL WITH A CARBONACEOUS REDUCING AGENT IN EXCESS OF 0.2 PART BY WEIGHT PER PART OF TITANIFEROUS MATERIAL AT A TEMPERATURE BETWEEN 1000* C. AND ABOUT 1500* C., COOLING AND COMMINUTING THE MASS, CHLORINATING THE RESULTING COMMINUTED MASS BY SUSPENDING THE SAME IN A GASEOUS CHLORINATING AGENT IN A FLUIDIZED REACTOR AT A TEM PERATURE MAINTAINED BETWEEN 200* AND 500* C.M WHEREBY THE TITANIUM CONTENT OF STHE MATERIAL IS CHLORINATED AND SELECTIVELY REMOVED WITH RESPECT TO SAID CONTAMINATES, AND CONDENSING THE RESULTING VOLATILE TICL4, THE LATTER BEING SUBSTANTIALLY FREE FROM SAID CONTAMINANTS OF THE ORIGINAL TITANIFEROUS MATERIALS. 